Prompt

Pick any exercise in Chapter 12 of the calculus textbook. Post the solution or your attempt. Discuss any issues you might have had.

What were the most valuable elements you took away from this course?

Exercise 12.3.6

Evaluate \(f_x(x, y)\) and \(f_y(x, y)\) at the indicated point.

\[f(x,y) = x^3 − 3x + y^2 − 6y\ at\ (−1,3)\]

Partial Derivatives

\(f_x\)

\[f_x(x,y) = 3x^2 − 3\] \[f_x(-1,3) = 3(-1)^2 − 3\]

\[f_x(-1,3) = 0\]

\(f_y\)

\[f_y(x,y) = 2y − 6\]

\[f_y(-1,3) = 2(3) − 6\] \[f_y(-1,3) = 0\]

Confirm with R

f_ <- expression(x**3 - 3*x + y**2 - 6*y) 
x <- -1
y <- 3

f_x <- D(f_, "x")
f_x
## 3 * x^2 - 3
f_y <- D(f_, "y")
f_y
## 2 * y - 6
eval(f_x)
## [1] 0
eval(f_y)
## [1] 0